Abstract: Unrefined steel is refined by the use of a refining slag in a furnace having two pressure-tightly interconnected, pressure-tightly covered upper and lower hearths having channeltype inductors for heating and stirring steel melts in the hearths, the refining being effected in the upper hearth only and which is of relatively small capacity and has its inductor tilted to effect vigorous melt flow. The refining is continued, batch after batch, with each batch transferred to the lower hearth which is of substantially larger capacity and where the refined steel can be held at a temperature lower than required for its refining, to obtain a volume of refined steel adequate for steel plant casting purposes. Gas pressure in the lower hearth maintains the melt level in the upper hearth as required during the refining, this gas pressure being lowered to transfer each batch of refined steel to the larger lower hearth, and then being increased again for the next refining operation.